Lubricating oil composition



' hot metal surfaces.

. ceeds.

Patented Feb. 29, 1944 UNITED sTATas VPATE nonmoe'rmc on. colurosmon RobertG. Larsen and Frederic A. Armfleld, Berkeley, CaliL, assls'nors to Company, San Francisco,

of Delaware No Drawing. Application Serial No.

'13 Claims.

' posit a finely-divided oil-insoluble carbonaceous material, commonly known as sludge. Under some conditions they may deposit a varnish on of inhibited oils is therefore very slow at fi-st and then experiences a break to a marked and surden increase. On the other hand, the type known as retarders are oxidized readily at first but increase their inhibiting powers as oxidation pro- Oxidation of oils containing retarders is therefore initially fast and then approaches an extended. stage where oxidation proceeds at a rather uniform, greatly reduced speed.

Inhibitor type compounds are best illustrated by the alkylated phenols, while retarder type compounds are illustrated by certain aromatic sulfur compounds such as dibenzyl disulflde. The

oxidized and lose their eflectiveness, while the disadvantage of the latter is that apparently they foster sludge formation.

Where certain selected stable aromatics actas;

inhibitors, retarders, or acombination of both.

, and render lubricating oils in which they are dissolved in small quantities less susceptible to attack by oxygen, the oxidation of the unstable constituents oi the refined oil proceeds competitively, or at a slowe rate than oxidation of the aromatic. Some aromatics such as alkylated naphthalene are so stable that they do not oxidiz apis that they are soon' Shell Development calm, a corporation July 29, 1941,

- propyl, -isopropyl; primary-, secondary-; or terdrocarbons which we preciably' in the presence of thevunstable .constituents little, it any, oxidation-inhibiting eflect.

Now it has been discovered that the addition oi products obtained by oxidizing stable alkyl-substituted aromatic hydrocarbons. free from polar radicals and having more than one condensed ring, to mineral lubricating oils in suitable small quantities, produces oxidation stablity.

useful anti-oxidant are either 1) the pure comgroups attached to the naphthalene nucleus, e. 3., naphthalene, alphaor beta-methyl, -ethyl, -iitiary-butyl, -amyl, etc.. naphthalenes; 1-2, 1-4,

methyl-ethyl, methyl-propyL- methyl-isopropyl, 'di-isopropyl, methyl-butyl, isopropyl-tertiarybutyl, (ii-primary, -secondary, or tertiary butyl, di-prima secondary or tertiary amyl, etc., tri tetra penta, etc.,' alkyl naphthalenes or corresponding alkylated anthracenes; phenanthrenes,

and other highly condensed aromatics. etc; or (2) highly aromatic relatively high-boiling frac- ,tions 01 coking cycle stocks, a substantial por- To make these aromatic tion of whichboils above 240 obtained by operating a liquid: phase cracking and before removing the latter.

v Less desirable but also useful are high-boiling vapor phase cracked or other highly aromatic hydrocarbon distillates, by extracting kerosenes.

hydrocarbons, providing such distillates are sufliciently aromatic and free 01' olefins, e. g. containing at least 50% of aromatics.

fractions free of sludgeforming propensities, are often removed by sulfuric acid, aluminum chloride, clays, or other treating agents. j

The aromatic hydrocarbons discussed herein as much as possi' ble. lazy-oxidize with hydrogen peroxide, manganese xide, permanganates, chlorates, perchlorates, perborates, cro-. mates,,chromic acid, etc., preferably under conditions that will not cause ring cleavage and if desired in the presence of catalysts that tend to destroy organic peroxides.

f 2,343,125 NT OF ICE] found in refined oils and therefore have lubricating oils of improved The stable alkylatd multi-nucleararomatic hymay oxidize to form our I having one or more alkyl such as extracts produced sa's oils, etc with seelective solventshaving preferential solvent power tor aromatic sulfur and other impurities treating th distillate with,

2 I a,ses,ias

our preferred method consists of passing gasscribed before may be further improved by the cons oxygen at atmospheric or higher pressures addition of wax suppressors such as pour point through the aromatic hydrocarbons at temperaor cloud point deprcssors, blooming agents, ex-, tures between 110' C; and 250 C. and preferably treme pressure agents, anti-wear agents, cormbetween 140 C. to 180 C. This temperature a alon inhibitors, and other compounding ingredirange is desirable, inasmuch as it permits fairly ents.

rapid oxidation under conditions at which per- We claim as our invention:

oxides are comparatively unstable with the re- 1. Alubricating composition comprising a minsult that an oxidized material is obtained, coneral hydrocarbon oil and dissolved therein. a taining few ,if any peroxides. i minor amount of a pro-oxidised aromatic hydrov The degree of oxidation may, at any point. be carbon mixture obtainedby oxidation unde'r eondetermined by either one of two convenient ditions to suppress ring cleavage and peroxide methods. The first method consists of withdraw- 7 formation comprising passing gaseous oxygen ing a and fractionally distilling it to dethrough said aromatic hydrocarbon mixture at termine the amount of unoxidizcd material boilit temperatures between about 110 and 250 C. and ing at the temperature of the original untreated at at least atmospheric pressure, said hydrocararomatic hydrocarbons. The second method, apbon mixture'being free from olenns, and complicable when oxidizing with free oxygen, conprising predominantly aromatic hydrocarbons sists of determining the total absorption of free having at least 2 condensed rinl said oxidized omgen, and collecting and measuring quantities 2o mixturecontaining asubstantial amount of ox-. of carbon dioxide and water evolved in the course idized components. -of the oxidation, the amount of oxygen intro- 2. A lubricatin compo tio mp in a i duced into the hydrocarbons being calculated by oral lubricating oil and dissolved therein 'a minor difference. Thus the degree of oxidation may be amount of a pro-oxidized aromatic hydrocarbon expressed in percent of hydrocarbons oxidised. or mixture obtained by oxidation under conditions 'in percent of oxygen content of the oxidized hyto ppr ri eava a p r x e formadrocarbons. The two methods of expressing the tion comprising passi g gaseous oxygen throu h oxygen content can approximately be correlated aid ar m t b b n mix t t mp raby determining the average molecular weight of hir een ab ut 110 and 250 C. and at at the hydrocarbons; Thug I least atmospheric pressure. said hydrocarbon mixture being free from oiefins, and comprising 1 im m X m predominantly alkyl substituted aromatic hydrohydroc n carbons having at least 2 condensed rings, said The extent of oxidation is preferably such 7 Oxidized mi 6011mm!!! 8l11b6t8nt19-1 i -m im that about 5 to 50% ofthe hydrocarbon materiso di mp e ts. als have been iddised. I: desired, however, low- A u cati compos tion comprising a miner or higher percentage of oxidized compon nts eral lubricating oil and dissolved therein a minor are permissible. As already indicated, the peramount of a D w aromatic hydro b oxide content should be as low as possible. prcfmixture obtained by x t n und r ond tions erably lessthan about 1% of the oxidized hydroto suppr ring cleavage and peroxide formation carbon although there is no critical limit for pri gaseou oxy n throu h s i this amount. In generai', the higherthc peroxa m y 8 mixture a tinnii ratur ide content, the poorer are the anti-oxidant propbetween abou 110 a d 5 and at at least, erties of the oxidized hydrocarbons. t o p c press sa d h dr a bon mi ture The following example further illustrates our bein -fre m efl and comprising r om j invention. In the table below are presented the tly olkyl Substituted ar m i hydrocarbons induction periods of an uninhibited pure hYd1'0- h ving at least '2 condensed ring said di carbon oil, the lwdrocarbon oil plus unoxidiaed mix tainin twe 5% and by secondary-amyl-naphthalene and alpha-'methyl- Weight 0! 011111886. pon n naphthalene and the hydrocarbon oil plus iden- A l ati composition comprisin a mintical percentages of the corresponding oxidized r lu r atin o l an di lved therein .a minor compounds which had been oxidized until they a ount o a p -ox di e ar atic hyd ocarb n contained 1.7% and 1.2% by weight or absorbed mixture obtained by oxidation under conditions oxygen or 29.7% and 10.8% of oxidized com oto suppre ri cleava s dp ro d fo anents respectively, I tlon, comprising passing gaseous oxygen through Table said aromatic hydrocarbon mixture at temperatures between about 110 25.0 C. and at at least atmospheric pressure, said hydrocarbon Time to Hydroabsorb mixture being free fromolei'lns and comprising 5g Added We :gfghfg, predominantly aim substituted aromatic hydrotar c. carbons having at least 2 condensed rings, said oxidized mixture containing. between 10% and on Haws 4 20% by weight of oxidized components. e its r mhtt m m t mbre s sec.-amy -nsp l1 0 V therein ggl t g I zffl ulpum r -n o 2333 a. minor amount of a pro-oxidised aromatic hyens... 4- drocarbon mixture obtained by oxidation under conditions to suppress ringcieavage and perox- The preferred amounts of our oxidized aroide formation com rising passing gaseous oxymatic motions to be added to lubricating oils gen through said aromatic hydrocarbon mixture range from 2% to 10% by weight of theoil, alat temperatuhes between about and 250 C. though in most instances amounts within the and at atleastatmospheric pressure. said hydrorange oi 5%, to 15%. may be used. r carbon mixture-being free from olefins, and com- Lubricating, 31181011118110! turbine oils conprising predominantly cracked hi h ar ti taining. our oxidized aromatic hydrocarbons dehydro arbon distillat said oxidised mixture con- 6. A lubricating oil composition comprising a mineral hydrocarbon oil and dissolved therein a minor amount of a p're-oxidized aromatic hydrocarbon mixture obtained by oxidation under conditions to suppress ring cleavage and peroxide formation comprising passing gaseous oxygen through said aromatic hydrocarbon mixture at temperatures between about 110 and 250 C. and at at least atmospheric pressure, said hydrocarbon mixture being free from oleflns, and comprising predominantly alkyl naphthylene said oxidizing, mixture containing a substantial amount of oxidizing components.

7. A lubricating oil compositiont comprising a mineral hydrocarbon oil and dissolved therein a minor amount of a pre-oxidized aromatic hydrocarbon mixture obtained by oxidation under conditions to suppress ring cleavage and peroxide formation comprising passing gaseous oxygen through said aromatic hydrocarbon mixture at temperatures between about 110 and 250 C. and at at least atmospheric pressure, said hydrocarbon mixture being free from olefins and comprising predominantly methyl naphthylene, said oxidizing mixture containing a substantial amount of oxidizing components.

8. A composition relatively stable to oxidation comprising a refined relatively viscous mineral oil subject to deterioration by oxidation and dissolved therein a small amount of a pre-oxidized aromatic hydrocarbon mixture obtained by oxidation under conditions to suppress ring cleavage and peroxide formation comprising passing gaseous oxygen through said aromatic hydrocarbon mixture at temperatures between about 110 and 250 C. and at at least atmospheric pressure, said hydrocarbon mixture being free from olefins and comprising predominantly aromatic hydrocarbons having at least 2 condensed rings, said oxidized mixture containing a substantial amount of oxidized components.

9. The method of inhibiting the oxidation of a mineral lubricating oil normally susceptible to deterioration by oxidation comprising. passing gaseous oxygen through an aromatic hydrocarbon mixture at a temperature between about 110 and 250 C. and at at least atmospheric pressure so as to suppress ring cleavage and formations of peroxides, said hydrocarbon mixture being free from oleflns and comprising predominantly aromatic hydrocarbons having at least 2 condensed rings, and adding a minor amount of the resulting oxidized material to a larger amount of said lubricatingoil.

10. The composition of claim 1 wherein said organic hydrocarbon mixture is oxidized at a temperature between about 140 and 180 C.

11. The composition of claim 3 in which the amount of the preoxidized mixture is from .5%

to 15% by weight of the oil.

12. The composition of claim 3 in which the amount of the preoxidized mixture is from 2% to 10% by weight of the oil.

13. The composition of claim 1 wherein the peroxide content of the preoxidized hydrocarbon is less than about 1% of -its oxidized components.

. ROBERT G. LARSEN.

FREDERIC A. ARMF'IELD. 

